The goal of this project is to provide an evidence-based approach to guide repeated mass antibiotic treatments in trachoma control. Trachoma remains the leading cause of infectious blindness. The cause of trachoma, ocular Chlamydia infection, is cleared with a single dose of azithromycin. However, given the community pool of Chlamydia, re-infection after treatment is common. Therefore, mass azithromycin treatment has been advocated to reduce the community pool of ocular Chlamydia. An NEI-funded trial is currently underway in Ethiopia to test the efficacy of different treatment strategies for trachoma, using mass antibiotic distributions. Nonetheless, much is still unknown about mass antibiotic distributions for trachoma. Using the data collected during this clinical trial, I will address the following specific aims: 1) To determine the relationship between clinical signs of trachoma and laboratory evidence of Chlamydia infection after antibiotic treatment. 2) To determine community predictors of post-treatment prevalence of ocular Chlamydia. 3) To determine the cost-effectiveness of different treatment strategies for trachoma. My career development plan includes didactics and mentorship. I plan on courses in epidemiology, biostatistics, and health economics at UCSF during the first 2 years of the grant. I will concentrate on data analysis during the remaining 3 years, with excellent mentors at UCSF: Drs. Thomas Lietman, Todd Margolis, George Rutherford, and Dean Jamison. My short term goal is to become an independent researcher in epidemiology and health economics, with a focus on developing countries. My long term goal is have a successful, productive career as an academic ophthalmologist and epidemiologist. RELEVANCE: Trachoma research can influence public health programs relatively quickly, through the advocacy of the World Health Organization. The proposed research will help trachoma programs to decide whether or not to continue mass antibiotic treatments, to decide which communities to target for treatment, and to decide how to allocate their limited resources.